Iris-class cruiser

The Iris-class ships were designed as dispatch vessels by William White under the direction of Nathaniel Barnaby, Director of Naval Construction, and were later redesignated as second-class protected cruisers. The only visible difference between the sister ships was that {{HMS|Iris|1877|2}} had a clipper bow and was longer than {{HMS|Mercury|1878|2}} with her straight stem. Iris was {{convert|331|ft|6|in|m|0}} long overall while Mercury was {{convert|315|ft|m|0}} long. The sisters had a beam of {{convert|46|ft|m|0}}, and a draught of {{convert|20|ft|6|in|m|1}}. They displaced {{convert|3730|LT|t|lk=on}} at normal load and were the first British warships with an all-steel hull.Gardiner, p. 90 Their crew consisted of 275 officers and ratings.Lyon & Winfield, p. 270 The ships were not armoured but extensive internal subdivision gave them some protection against flooding, as did the {{convert|150|ft|m|1|adj=mid|-long}} double bottom under the propulsion machinery compartments.

The Iris class was powered by a pair of horizontal four-cylinder Maudslay, Sons and Field compound-expansion steam engines that were configured with a pair of high-pressure cylinders with a bore of {{convert|41|in|cm}} and a pair of low-pressure cylinders {{convert|75|in|cm}} in diameter. All cylinders had a {{convert|36|in|cm|adj=on}} stroke. Each engine drove one propeller shaft using steam from eight oval and four cylindrical boilers with a working pressure of {{convert|65|psi|kPa kg/cm2|0|abbr=on|lk=on}}. The engines were designed to produce a total of {{convert|6000|ihp|lk=on}} for a speed of {{convert|17|kn|lk=in}}, which was handily exceeded by the sisters. Iris initially reached a maximum speed of {{convert|16.6|kn}} from {{convert|7086|ihp|abbr=on}} during her sea trials, but after new propellers were fitted, achieved {{convert|17.89|kn}} from {{cvt|7330|ihp}}. Mercury became the fastest warship in the world when she made {{convert|18.57|kn}} from {{cvt|7735|ihp}}.Roberts, p. 74 The ships carried a maximum of {{convert|780|LT|t|0}} of coal, enough to steam {{convert|4400|-|4950|nmi|lk=in}} at {{convert|10|knots}}. They were initially fitted with a barque sailing rig, but this was removed after a few years.

The Iris-class ships were originally armed with ten 64-pounder ({{convert|6.3|in|adj=on}}) rifled muzzle-loading (RML) guns, eight on the main deck and the remaining pair on the upper deck on pivot mounts to serve as chase guns fore and aft.

Iris was launched in 1877 and sold in 1905 while Mercury, launched a year later, was hulked at Chatham in 1914 and sold for scrap in 1919.

{{Reflist}}

{{Commons category|Iris class cruiser}}

• {{cite book|editor-last1=Gardiner|editor-first1= Robert|title=Steam, Steel and Shellfire: The Steam Warship 1815–1905|series=Conway's History of the Ship|year=1992|publisher=Conway Maritime Press|location=London|isbn=1-55750-774-0}}
• {{cite book |last1=Lyon |first1=David |last2=Winfield |first2=Rif |title=The Sail & Steam Navy List: All the Ships of the Royal Navy 1815–1889 |date=2004 |publisher=Chatham Publishing |location=London |isbn=1-86176-032-9|name-list-style=amp}}
• {{cite book|title=Conway's All the World's Fighting Ships 1860–1905|editor-last1=Gardiner |editor-first1=Robert|publisher=Conway Maritime Press|location=Greenwich|year=1979 |isbn=0-8317-0302-4 |url-access=registration|url=https://archive.org/details/conwaysallworlds0000unse_l2e2|chapter=Great Britain|last1=Roberts|first1=John}}

{{Iris class cruisers}}

Category:Cruiser classes

Category:Ship classes of the Royal Navy